Investigations are being conducted on the events leading to the formation of several types of cataract. Diabetic or sugar cataract formation initiated by the enzyme aldose reductase is being studied; moreover, the relationship between aldose reductase and other ocular diabetic complications such as retinopathy, corneal epitheliopathy, and basement membrane thickening is being investigated. Methods of delaying the onset of these complications through the pharmacological control of aldose reductase are also being developed. The potential role of the enzyme pyrroline-5-carboxylate reductase in cataractogenesis is also being investigated. This enzyme, which possibly regulates cellular redox potentials and increases ATP levels through stimulation of the pentose shunt, is involved in the metabolic conversion of ornithine and glutamine to proline. Hereditary cataract formation is also being studied in a strain of mice developed in our laboratory. These animals known as Philly mice develop osmotic cataracts by an as yet unknown mechanism.